Most of the human studies supported by the TTURC entail the recruitment of subjects with a validated history of tobacco use. Some require documentation of abstinence either as a component of the study, or, in treatment trials, as a measure of outcome. Some require adminstration of nicotine, and others, various drugs, either as probes of nicotine's action, or as potential therapies in smoking cessation trials. All benefit from access to drug concentrations as an objective measure of drug exposure. The core laboratory will measure concentrations of cotinine in serum or urine as an objective measure of chronic nicotine exposure and marker of extended abstinence. These measures are essential to reliably quantify prior tobacco exposure in conjunction with subject recruitment, assure concordance between treatment arms, and to reliably document abstinence as an outcome in treatment studies or for investigations into the mechanisms of abstinence and relapse. Serum nicotine measurements by the core laboratory will allow for acute measurement of nicotine exposure, document acute abstinence, and for nicotine administration studies, help to account for interindividual differences in drug disposition. Similarly, measurement of concentrations of drugs in smoking cessation studies will allow an objective assessment of compliance. Knowledge of plasma concentrations may also help to explain variations in response and/or toxicity. Measurement of drugs used to acutely probe or perturb pathways involved in nicotine's actions will allow assessment of possible differences in drug exposure between treatment groups. The core laboratory provides a transdisciplinary pharmacology/drug esposure perspective to studies otherwise focused on behavior and/or neuroscience, and can also enhance the informational value of such studies beyond that of the primary goals of the investigation. Since common methodology and targets for analysis are used to support multiple projects, there are opportunities to integrate data across studies.